Action potential 0.0 / 5 ? BiologyHealth, illness and diseaseA2/A-levelEdexcel Created by: francesca_321Created on: 03-02-16 18:17 What do neurons have on their surface membranes? sodium-potassium pumps 1 of 27 What do they pump out? sodium ions by active transport 2 of 27 how many sodium ions are moved out? three 3 of 27 How many potassium ions are moved in? 2 4 of 27 What are there in the membrane that allow the passage of sodium? channels 5 of 27 What happens at rest? A few K+ channels are open 6 of 27 What are potassium ions able to do? diffuse back out of the cell, down their concentration gradient 7 of 27 As a result, What does the neurone have? more positive ions outside than inside 8 of 27 What is there a potential difference across? the axon membrane with a charge of about 70mV 9 of 27 What is this called? resting potential 10 of 27 What happens when a receptor receives a stimulus? It can cause a different set of sodium channels to open 11 of 27 What does this allow the sodium ons to do? flood into the cell 12 of 27 Down the? electrochemical gradient 13 of 27 What does this rapidly reverse? potential difference across the cell membrane 14 of 27 What does this make it? less negative inside 15 of 27 The neurone is what> Depolarised 16 of 27 What do the sodium ions continue to do? Until ? flood the cell until it has become positive inside 17 of 27 reaching what voltage? +30mv 18 of 27 What happens at this voltage? The sodium ion channels then close 19 of 27 What does this change in potential difference across the membrane also causes what? a number of potassium ion channels to open 20 of 27 What channels are these? voltage-gated channels 21 of 27 Why? they open when the potential difference across the membrane is positive inside 22 of 27 What can potassium ions now do? flood out of the axon, down their electrochemical gradient 23 of 27 What does this make? the chage inside less positive 24 of 27 What does this drop to? down to a little below the value of the resting potential 25 of 27 AKA? hyperpolarisation 26 of 27 What is this time taken for the axon to restore its resting potential called? refractory period 27 of 27
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